It is known to place a contact lens onto the eye to view the fundus of the eye. The contact lens makes it possible to view image sections of up to 20.degree. on the fundus. Furthermore, a so called "Panfunduscope" is known, which enables a view of up to 150.degree. of the fundus. However, a disadvantage of this known panfunduscope is that it requires a placement directly onto the eye. This makes complicated resetting operations necessary during surgeries, which must be carried out both in front of the eye lens and also behind the eye lens, so that both surgeries can be carried out with one surgery stereomicroscope. When using only one contact lens, this is avoided, however, the obtained 20.degree. image section is relatively small, so that the microscope must often be reset, which is also disadvantgeous during such surgeries.
The basic purpose of the invention is to provide an attachment for microscopes, in particular for stereomicroscopes for facilitating a contact-free viewing of the abovementioned type, which can be attached easily and quickly to the microscope or to the stereomicroscope and which delivers an image section of up to 120.degree. and permits a free movability of the eye and which most importantly can be quickly sterilized at high temperatures, without influencing the wearability of the attachment.
Thus the attachment consists according to the invention of two lenses or lens systems, the distance between which can be adjusted for the purpose of compensating for the sight deficiency of an eye of the patient- and which can be connected to the stereomicroscope through a screw or bayonet coupling. The two lenses of the attachment replace the lens of the stereomicroscope. The outer lens, that is the lens, which is opposed to the eye of the patient to be operated on, can be moved easily in axial direction of the attachment, so that also during an unintended movement of the eye by the patient, the lens gives way or yields and thus the eye cannot suffer damage. All reciprocally movable parts of the attachment are provided with a coating consisting of pressed and sintered PTFE polymers containing Al.sub.2 O.sub.3 particles.
The attachment can thus be easily inserted into existing surgery microscopes and is advantageously provided with a quick-change mechanism, with which selectively the present objective of the stereomicroscope or, however, the attachment can be swung into the beam path of the stereomicroscope. This makes it possible to create an image of the front eye section through the normal objective and during a swinging over to the contact-free wide-angle system of the fundus of the eye. The system is optically tuned such that during this back and forth swinging, a sharp image is obtained both on the front and also on the rear eye section without any adjustment, if the patient is ametropic. For nonametropic patients, the upper system for the wide-angle viewing is constructed adjustably, so that a suitable refocussing can take place.
The lower adjustable system is according to the invention provided with a thread, into which a safety mechanism engages, which prevents a complete removal or disengagement, which can lead to accidents. The inventively suggested coating of the attachment has a temperature stability of up to 250.degree. C., so that the complete system can be sterilized easily at least at 160.degree. C. This coating has moreover the advantage that the mechanical antifriction properties are not lost during sterilization, so that an easy sliding of the parts in one another and also the movability of the outer lens in axial direction of the attachment is maintained without any interference even after several sterilizations. Fats and lubricants, as they are needed otherwise to obtain the easy motion between the individual parts, are not needed here.
The outer lens is constructed preferably completely exchangeably, so that here lenses for variable focuses can be used, so that differently large image sections can be obtained.
According to a preferable embodiment, the image changer, in which both the attachment and also the normal objective lens of the microscope are arranged, is provided with a motor, so that a quick change between both optical systems is possible.
It is common in some hospitals to hang a sterile plastic sack over the complete microscope, which is usually placed onto the objective lens attachment. This plastic sack can also be used with the wide-angle attachment through a changed adaptor. In addition, it is possible to moe from below a sterile plastic part onto the attachment, so that the sterility of the entire system is maintained.